1. Field of the Invention
The present invention relates to a gear ratio control device, a method for controlling gear ratio, and a vehicle.
2. Discussion of the Background
As described in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-502543, there is known, as a conventional automobile drive system, a hybrid type drive system configured such that an engine and transmission and motor generator are combined, with a drive shaft of the transmission and a driven shaft are connected by an eccentric member driving device provided to the drive shaft and a one-way clutch provided to the driven shaft, so that output of the engine is supplied to the drive shaft of the transmission. Also, the motor generator is selectively connectable to the input side of the transmission or the output side of the one-way clutch via a clutch, or simultaneously connectable to the input side of the transmission and the output side of the one-way clutch.
With this drive system, engine driving using just the driving force of the engine, EV (electric vehicle) driving using just the driving force of the motor generator, and parallel driving using both the driving force of the engine and the driving force of the motor generator, can be performed. Note that the engine can be started with the motor generator.
The transmission used with this drive system is a continuously variable transmission called IVT (Infinity Variable Transmission) of a type which converts rotational motion of a drive shaft into oscillating motion, and further converts the oscillating motion into rotational motion which is output from a driven shaft. With transmissions of this type, the gear ratio can be changed nonstop without using a clutch, and the maximum value of the gear ratio can be set to infinity. Note that with this transmission, the number of output revolutions when the gear ratio is set to infinity is zero.
FIG. 6 is a side cross-sectional view of the configuration of a portion of a continuously variable transmission called an IVT, viewed from the axial direction. The continuously variable transmission in FIG. 6 includes an input shaft 101, which rotates on an input center axial line O1 under rotational force from a power source such as an internal combustion engine or the like, an eccentric disc 104 integrally rotating with the input shaft 101, a linking member 130 to connect the input side and output side, and a one-way clutch 120 provided on the output side.
The eccentric disc 104 is formed circularly with a first support point O3 as the center. The first support points O3 are provided at equal intervals in the circumferential direction of the input shaft 101, the eccentricity r1 of each as to the input center axial line O1 being changeable, so as to rotate around the input center axial line O1 along with the input shaft 101 while maintaining the eccentricity r1. Accordingly, the eccentric disc 104 is provided so as to eccentrically rotate around the input center axial line O1 in accordance with the rotation of the input shaft 101, while each maintaining the eccentricity r1.
As shown in FIG. 6, the eccentric disc 104 is configured of an outer circumference side disc 105, and an inner circumference side disc 108 which is integrally formed with the input shaft 101. The inner circumference side disc 108 is formed as a thick disc, with the center thereof displaced by a certain eccentric distance as to the input center axial line O1 which is the center axial line of the input shaft 101. The outer circumference side disc 105 is formed as a thick disc centered on the first support point O3, and has a first circular hole 106 of which the center is away from the center of the outer circumference side disc 105, i.e., away from the first support point O3. The outer circumference of the inner circumference side disc 108 rotatably fits with the inner circumference of the first circular hole 106.
Also, a second circular hole 109 is formed to the inner circumference side disc 108, being centered on the input center axial line O1 and having a portion in the circumferential direction thereof opened to the outer circumference of the inner circumference side disc 108. A pinion 110 is rotatably contained within the second circular hole 109. The teeth of the pinion 110 mesh with an annular gear 107 formed on the inner circumference of the first circular hole 106 of the outer circumference side disc 105, through the opening on the outer circumference of the second circular hole 109.
This pinion 110 is provided so as to rotate coaxially with the input center axial line O1 which is the center axial line of the input shaft 101. That is to say, the center of rotation of the pinion 110 and the input center axial line O1 which is the center axial line of the input shaft 101 match. The pinion 110 is rotated within the second circular hole 109 by an unshown actuator configured of a DC motor and a reducer. Normally, the pinion 110 is rotated synchronously with the rotation of the input shaft 101, and with the synchronized revolutions as a reference, the pinion 110 is caused to rotate relative to the input shaft 101 by providing the pinion 110 with revolutions greater than or less than the revolutions of the input shaft 101. For example, this is realized by the pinion 110 and output shaft of the actuator being situated so as to be mutually linked, and in the event that there is rotational difference between the rotations of the actuator as to the rotations of the input shaft 101, a reducer (e.g., a planetary gear) is used whereby the relative angle between the input shaft 101 and the pinion 110 changes by an amount equivalent to the rotational difference multiplied by the ratio of reduction. At this time, in the event that the actuator and the input shaft 101 are synchronized with no rotational difference, the eccentricity r1 does not change.
Accordingly, by turning the pinion 110, the annular gear 107 with which the teeth of the pinion 110 mesh, i.e., the outer circumference side disc 105, rotates relative to the inner circumference side disc 108, whereby the distance between the center of the pinion 110 (input center axial line O1) and the center of the outer circumference side disc 105 (first support point O3), i.e., the eccentricity of the eccentric disc 104 changes.
Settings have been made such that, in this case, the center of the outer circumference side disc 105 (first support point O3) can be made to match with the center of the pinion 110 (input center axial line O1) by rotating the pinion 110, and by matching these centers, the eccentricity r1 of the eccentric disc 104 can be set to zero.
Also, the one-way clutch 120 includes an output member (clutch inner) 121 which rotates around an output center axial line O2 which is away from the input center axial line O1, a ring-shaped input member (clutch outer) 122 which oscillates around the output center axial line O2 upon external force in the rotational direction be applied thereupon, multiple rollers (engaging units) 123 inserted between the input member 122 and output member 121 to place the input member 122 and the output member 121 in a mutually locked state or unlocked state. Note that rollers 123 of a number equal as the number of cross-sectional sides of the output member 121 are provided to the one-way clutch.
Transmission of power (torque) from the input member 122 of the one-way clutch 120 to the output member 121 thereof is performed only under the condition that the rotational speed of the of the input member 122 in the positive direction (e.g., the direction indicated by arrow RD1 in FIG. 6) exceeds the rotational speed of the output member 121 in the positive direction. That is to say, only in the event that the rotational speed of the input member 122 exceeds the rotational speed of the output member 121, does meshing (locking) occur via the rollers 123, and the oscillating motion of the input member 122 is converted into rotational motion of the output member 121.
One protruding portion 124 is provided in the circumferential direction on the ring-shaped input member 122, with a second supporting point O4 distanced from the output center axial line O2 being provided to the protruding portion 124. A pin 125 is situated on the second supporting point O4 of each input member 122, and a tip (other end portion) 132 of the linking member 130 is rotatably linked to the input member 122 by the pin 125.
The linking member 130 has a ring portion 131 at one end side, with the inner circumference of a circular opening 133 of the ring portion 131 rotatably fitting the outer circumference of the eccentric disc 104 via a bearing 140.
Accordingly, one end of the linking member 130 is rotatably linked to the outer circumference of the eccentric disc 104, and the other end of the linking member 130 is rotatably linked to the second supporting point O4 provided on the input member 122 of the one-say clutch 120, whereby a four-bar linkage mechanism, with the four joints of input center axial line O1, first support point O3, output center axial line O2, and second supporting point O4 serving as turning points being, is configured as shown in FIG. 7.
FIG. 7 is an explanatory diagram of the driving force transmission principle of the continuously variable transmission configured as a four-bar linkage mechanism. With this four-bar linkage mechanism, rotational motion provided form the input shaft 101 to the eccentric disc 104 is transmitted to the input member 122 of the one-way clutch 120 as oscillating motion of this input member 122, and the oscillating motion of the input member 122 is converted into rotational motion of the output member 121. When the input shaft 101 rotating the eccentric disc 104 makes one rotation, the input member 122 of the one-way clutch 120 makes one reciprocal oscillation. The oscillation cycle of the input member 122 of the one-way clutch 120 is constant, regardless of the value of the eccentricity r1 of the eccentric disc 104, as shown in FIG. 7. The angular speed ω2 of the input member 122 is determined by the rotational angular speed ω1 of the eccentric disc 104 (input shaft 101) and eccentricity r1.
At this time, the eccentricity r1 of the eccentric disc 104 can be changed by moving, with the actuator, the pinion 110 of a variable gear ratio mechanism 112, configured of the pinion 110, the inner circumference side disc 108 having the second circular hole 109 containing the pinion 110, the outer circumference side disc 105 having the first circular hole 106 for rotatably containing the inner circumference side disc 108 and the actuator, and so forth. By changing the eccentricity r1, the oscillation angle θ2 of the input member 122 of the one-way clutch 120 can be changed, and accordingly, the ratio of revolutions (gear ratio, also written as “ratio i”) of the output member 121 as to the rotations of the input shaft 101 can be changed. That is to say, by adjusting the eccentricity r1 of the first support point O3 as to the input center axial line O1, the oscillation angle θ2 of the oscillation motion transmitted from the eccentric disc 104 to the input member 122 of the one-way clutch 120 is changed, whereby the gear ratio at the time of the rotational force input to the input shaft 101 being transmitted to the output member 121 of the one-way clutch 120 as rotational force via the eccentric disc 104 and linking members 130 can be changed.
FIGS. 8A through 9C are explanatory diagrams of a transmission principle with the variable gear ratio mechanism 112 at the continuously variable transmission shown in FIG. 6. As shown in FIGS. 8A through 9C, the eccentricity r1 of the eccentric disc 104 as to the input center axial line O1 (center of rotation of the pinion 110) can be adjusted by rotating the pinion 110 of the variable gear ratio mechanism 112 to rotate the outer circumference side disc 105 as to the inner circumference side disc 108.
For example, as shown in FIGS. 8A and 9A, in the event that the eccentricity r1 of the eccentric disc 104 is set to “great”, the oscillation angle θ2 of the input member 122 of the one-way clutch 120 can be made greater, so a small gear ratio i can be realized. Also, as shown in FIGS. 8B and 9B, in the event that the eccentricity r1 of the eccentric disc 104 is set to “medium”, the oscillation angle θ2 of the input member 122 of the one-way clutch 120 can be set to “medium”, so a medium level gear ratio i can be realized. Further, as shown in FIGS. 8C and 9C, in the event that the eccentricity r1 of the eccentric disc 104 is set to “small”, the oscillation angle θ2 of the input member 122 of the one-way clutch 120 can be made smaller, so a great gear ratio i can be realized. Moreover, as shown in FIG. 8D, in the event that the eccentricity r1 of the eccentric disc 104 is set to “zero”, the oscillation angle θ2 of the input member 122 of the one-way clutch 120 can be set to “zero”, so a gear ratio i of infinity (∞) can be realized.
The oscillation cycle of the input member 122 of the one-way clutch 120 is constant, regardless of the value of the eccentricity r1 of the eccentric disc 104, as shown in FIG. 10. FIG. 6 is a side cross-sectional view and accordingly only illustrates one set of the eccentric disc 104, linking member 130, and one-way clutch 120, but multiple sets of these are arrayed along the input center axial line O1 with an IVT. Note however, that each eccentric disc 104 in each set is formed with a circular form centered on a first support point O3, and the first support points O3 are arrayed at equal intervals in the circumferential direction around the input center axial line O1. Accordingly, the eccentric discs 104 perform eccentric rotation around the input center axial line O1 while maintaining the eccentricity r1, so oscillating motion brought about at the input member 122 of the one-way clutch 120 by the rotational motion of the eccentric discs 104 occurs in order with a certain phase, as shown in FIG. 11.
After driving by one linking member 130 has ended, the rotational speed of the input member 122 drops below the rotational speed of the output member 121, and also the locking by the rollers 123 is disengaged by the driving force of another linking member 130, thus returning to a free state (spinning state). By this being performed by all of the linking members 130 in order, the oscillating motion is converted into one-directional rotational motion. Accordingly, only the force of the input member 122 at a timing at which the rotational speed of the output member 121 is exceeded is transmitted to the output member 121 in order, and rotational force smoothed to being nearly flat is provided to the output member 121.